Prime mover supplied by gas generators



March 28, 1950 Filed Nov. 5, 1947 J. P'. CHITTENDEN ET AL I 2,502,127

PRIME MOVER SUPPLIED BY GAS GENERATORS 5 Sheets-Sheet l IINVENTORS: JOHNP. CHITTENDEN ROBERT J. WELSH Attorneys March 28, 1950 J. P. CHlTTENDE-NETAL PRIME-MOVERSUPPLVIED BY GAS GENERATORS 5 s eets-sheet 2 uZEEh 5.542

Filed Nov. 3, 1947 I @Q 9 mm .52 9% N 2 mEkuBE INVENTORS: JOHN P.CHITTENDEN ROBERT J. WELSH YQMV/Jdcov Attorneys Marh 28, 1950 J.P.'CHITTENDEN ETAL 2 ,502,127 PRIME MOVEZRv SUPPLIED BY GAS GENERATORSFiled Nov. 5, 1947 5 Sheets-Sheet :5

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m-+ mm mm wv h mm mum mm INVENTORS:' CHITTENDEN ROBERT J. WELSH JOHN P.

Attorneys March 28, 1950 J. PRCHITTENDEN ETAL 2,502,127

PRIME MOVER SUPPLIED BY GAS GENERATORS Fi1 e d Nov. :s, 1947 5Sheet-Sheet 4 pl .Dl l 3 3 3 w 0000 EH \9 v-q dUU FIG. 4

INVENTORS: JOHN P. CHITTENDEN ROBERT J. WELSH By 0M 515M Attorneys March28, 1950 J. P. CHITTENDEN :1 AL 7- PRIME MOVER SUPPLIED BY GASGENERATORS Filed Nov. 3, 1947 5 Sheets-Sheet 5v "u w w 3,3 Rm 1 Q E q: Q2 5 I\' 6 0 k 2 q 03 Q L q 2. Q \1 k 1- 33 2 s Q Q Q3 397v va L:033492100 03349 said arrangements.

Patented Mar. 28, 1950 PRIME MOVER SUPPLIED BY'GAS GENERATORS JohnPicton Chittenden, Bournemouth, and Robert James Welsh, Rugby, England,assignors to The English Electric Company Limited, London, England, aBritish company Application November 3, 1947, Serial No. 783,768

, In Great Britain October 28, 1941 Section 1, Public Law 690, August 8,1946 Patent expires October 28, 1961 2 Claims.

This application is a continuation in part of our application Ser. No.463,676, filed October 28,

'1942, for Prime mover supplied by gas generators, now abandoned, andrelates to a plant comprising a gas turbine or other prime mover themotive fluid of which is gas supplied at the necessary pressure byindependent gas generator units. Such a gas generator unit consists ofan internal combustion engine and a compressor driven thereby. The gasutilised in the prime mover may be compressed air from the compressor orthe exhaust gas from the engine, or more usually the exhaust gas dilutedwith compressed air from the compressor. In the most usual arrangementthe compressor will act as a scavenging and charging pump for theinternal combustion enhereinafter used as including any of the aiore-The prime mover will be hereinafter described as a turbine since it willusually take this form but it will be understood that it may take otherforms.

A gas generator unit as hereinbefore described will usually have adefinite minimum power output and accordingly there will be a definiteminimum power below which it is not possible to run the turbine, andtherefore it is more convenient to provide two or more gas generatorunits which, at full load on the turbine, are all in operation to supplythe one turbine in common; The power input to the turbine can thenbereduced below a minimum corresponding to the sum of the minimum outputsof all the gas generator units by putting one or more of these units outof operation.

The present invention concerns a plant in-- cluding a plurality of gasgenerators supplying motive fluid to a turbine in common, a separatefuel regulator for each, and a speed governor actuated by theturbine-controlling the fuel regulators of all the gas generators (andhence their combined output) automatically in accordance with the loadon the turbine.

The turbine is most conveniently governed by The internal comthe saidspeed-governor acting in known manner to set in motion a mechanical,electrical or fluid pressure servo-motor on any deviation of turbinespeed from the desired value, the servo-motor acting to vary the inputto the turbine in a corrective sense. A governing arrangement of thiskind, usually employing a hydraulic servo-motor controlled by valvesdirectlyactuated by the governor, is widely used for the regulation ofsteam turbines and other prime movers and if used in this form withoutmodification would be substantially iscchronous. To give stability ofoperation it is, however, customary to provide the governor with a speedadjuster such that the turbine speed maintained by the governor actuallydecreases slightly with increase of load on the turbine according tosome desired drooping speedload characteristic. According to the presentinvention the speed regulator adjusts the governor in accordance withthecombined output for which the gas generators are adjusted, wherebythe governor tends to maintain a predetermined speedload characteristicof the turbine, no matter how many gas generators are in action, andprovides a governing system which avoids any given load corresponding totwo or more governed speeds according to the number of gas generators inservice. Without such means for adjusting the governor the latter wouldnot maintain a continuous smooth variation of speed with variation ofload over the whole range of operation of the turbine; if the governorwere set to give a particular speed-load characteristic with a certainnumber of gas-generators in operation, the stopping of one of thesegas-generators or the starting of an extra one would result in an abruptchange to another speed-load characteristic and hence an abrupt changeof turbine speed. The governor may be a loaded centrifugal governor andthe adjustment may consist in varying the loading of the governor.Alternatively the adjustment may consisting in varying the relativepositions of the governor and the switch, valve or other member actuatedthereby to set the servomotors in operation.

In order to be better understood and readily carried into effect theinvention will be described by way of example with reference to theaccompanying drawings of which:

Fig. 1a shows a part view of a modification of the control gearaccording to Fig. 1;

Fig. 2 shows in section a typical gas generator with auxiliary devicesfor starting and stopping, as used in the power plant according to Fig.1;

Fig. 2a shows one of these auxiliary devices, the master starting airvalve and its servo-motor. in section on a larger scale;

Fig. 3 shows another of these auxiliary devices, the running indicator,in section on an enlarged scale;

Figs. 4 to 6 show still another of these auxiliary devices, the timingvalve, in three difierent positions in section on a still larger scale;

Fig. '7 is a speed-load diagram comparing the improved characteristic ofthe plant according to the invention with the characteristic of planthitherto known.

Referring now to Fig. 1, a centrifugal governor I driven by the turbine39 is loaded by the spring 2. A valve 3 directly actuated by thegovernor can connect a supply pipe 4 to the pressure side of a source offluid on a decrease of turbine speed below a predetermined speeddependent on the governor loading, and to the sump of said source on anincrease of speed above a predetermined speed dependent on the governorloading; a separate distributing valve member a can be moved to connectpipe 4 alternatively through pipes 4a and 4b, or through pipes. and idor through a pipes 4e ands to the servo-motor I5 controlling one of thegas generators 3 I, 32 and 33.

The gas generators 3|, 32 and Marc compressors driven by internalcombustion engines all exhausting into the common supply pipe 29 goingto the turbine 30 which drives the speed governor I. It is assumed thateach engine is of the compression ignition type, the power output beingdetermined by the quantity of fuel injected per cycle of the enginewhich quantity is again determined by the well known and common type offuel pump device-26 adjusted by the servo-motors 6(Fig. 2) hence itfollows that the output of each gas generator is determined by theposition of and fluid pressure in the associated one of thevservo-motors 3;

The gas generators'3l, 32. and 33 are shown merely diagrammatically inFig. 1 but the gas generator 3i is shown in. Fig. 2 in section as ofconventional free piston type. This gas generator thus comprises twopistons movingtowards and away fromeach other and :each made up of aparttia" reciprocating in the engine cylinder 3Ib, a part Sic drawingair into the compressor cylinder Sid byway oiinletvalve 3! e andcompressing this air which is eventually discharged by way of velvet I fto the inlet ports 3 I g in the engine cylinder, and a part 31hreciprocating in the bufier cylinder Sij. The outlet ports 31k intheengine cylinder 3ib are connected through the exhaust pipe 29a to thesupply pipe 29 0f the turbine 36 (Fig. 1'). The fuel injector 3! Z inthe engine'cylinder 3 i b is suppliedby the common type of fuel.injection pump indicatedat' 26, the fuel regulating rack 260. of whichis re'ciprocated against theforceoithe control spring 26b by the pistonto of the fluid pressure servo-motor, 6. Thus, as .is well known, thequantityof fuel injected is determined by the force applied to therack-in opposition to the force exerted byspring 25b; hence the fuelsupplied is determined by the forceexerted on thepiston Ea.

For startingthe free pistons in motion after they have been at'rest,each gas generator is pro- 4 vided with a starting device, one typicalform of which is illustrated in Figs. 2, 2a, 3 and 4 to 6.

Starting air is admitted from a source of coinparatively unrestrictedsupply through pipe 6| (Figs. 2 and 2a) and the master starting airvalve 66 via pipe 62 to the timing valve 83 (Figs. 2 and 4.- to 6) andfrom there by pipes 23 through non-return valves 22 to the buffercylinders 3 I7.

The pressure side of a source of fluid (not shown) is connected throughpipe 42 (Figs. 2 and 3) through the running indicator 3?, the functlonof which will be explained later, to a system of pressure pipes I33which are connected with two hydraulic relays, the barring relay I32 andthe end of stroke indicator H5 and various other auxiliary appliances ofthe gas generator such as the hydraulic cylinders adapted to open thevent valves I21 in the heads of the cushion cylinders 3H against springbias, the barring cylinder 25 and the counter-servo-motor for the fuelpump 26 (Fig. 2).

Another system of pipes-tfi connects the two relays H52 and fist withone another and with the servo-motor cylinder 5 and a valve 2 m formedby a recess in the rod of the barring piston 24. From the servo-motorcylinder 6 this type is continued by a pipe 75 leading to the end of thehydraulic relay @9 of the servo motorEiS-for the master starting airvalve iifiand from Valve Z ta via pipe 48 to a side port of the saidrelay 45h The free piston assemblies 3 la, 3 to and 3 iii are linked inthe usual way by links l and a twoarmed lever ii pivoted on the enginebody from which the motion of the oscillatory valve 38 of the runningindicator 3? (Figs. 2 and 3) is derived.

One of the links 1 is also connected by link 2i to the bell crank lever26 that operates the cam for the operation of the fuel pump 2% and,through a link-I29, the'cam 43 for the control of the relay E35 and thetiming valve 53.

Referring now particularly to Fig. 3, the running indicator'operates asfollows:

In a rest" position such as shown, fluid pressure passes from pipe 42through one of the two branch pipes 42a or 42?) past the recess in oneof the pistons 39, 420' to the pipe I33 and reaches. also, through pipe38, the recessed portion of the piston valve 36, andfrom there, througheither port. 31a or (as shown) port 31b, the associated cylinder ofpiston 39 or (as shown) piston ii). The cylinderoi the other piston, forexample, of 39, as shown, is drained to the oil sump (not shown) throughits port 37a. It is clear from Fig. 3 that, if the position of .thepistons as, lil were reversed, or both pistons were in their right handposition, the connection of pipe I33 with the pressure fluid supply frompipe 42 would still subsist.

As soon, however, as the free piston assembly is reciprocating, thepiston valve 3G is oscillated through its link connection 28 with thefree piston assemblies. and consequently suflicient fluid pressure ispassed throughpipe. 38round the recess of valve. 36 andboth ports 37aandltl'l) to force both pistons 39 and 40 to the left against theirweakspringsi. Ports 3.1aand 31b are or a re stricted. vcrosssection anddo not allow the escape ofpressurejto the oil. sump quickly enough toaifect the building up of pressure inside the cylinders for the pistons39, 49. It is clear from Fig. 3 that in thisposition .of the runningindicator, pipe 133 is cut off from pipe 42, and is vented to theoil-sump at 31c past the recessed portions of both pistons 39.48 andtheoblique canal 37d in the body of the casing 31.

, If the gas generator comes to a standstill in any as. described, andacts on the left hand side of the small piston I pushing it to theright. This is possible because the pressure from another branch of pipeI33 pushes the tripartite piston I34 of the relay I35" from the positionshown in .Fig. 2 to a right-hand position in which the left .hand recessof piston I34 connects the right-hand side of relay I32 through pipe 46to the sump at .E, cam 43 being then out of the way of the roller at thefree end of piston. I34.

As soonas piston I33 moves to the right, it

connects pipe I33 with pipe I26 whereby the vent valves I21 of thecushion cylinders 3| are opened and the barring piston 24 is pushed to Ithe right-hand side against the bias of its spring 41. The rod of piston24 bears against a shoulder of one of the compressor pistons 3i c andbars it to a position near the outer dead centre position -to make theengine ready for starting. In doing so, cam 43 is moved by the linkageI, 2I, 29, I29

into the position shown in Fig. 2 and pushes the piston I34 into theleft hand position as shown,

in which oil pressure from pipe I33 is passed via pipe 46 to theright-hand side of the large piston -I3I of relay I32, overriding theequal pressure on the small piston I39 and thus moving the pistons I30,I3I to the left-hand position in which they are shown. Pipe I26 is thusconnected to the sump at E, and the vent valves I2! are allowed toclose, and the barring piston 24 to be retracted by their respectivebiassing springs.

The engineis now set for starting which may on its underside.

be efiected manually as will be described first, or

automatically according to the invention as will be described later. Ifthe operator pushes piston 59 (Fig. 2a) of the relay 49 to the left bymeans 59 and lifts it off its seat in the master air valve casing 60thus admitting air pressure from pipe 6| through pipe 62, timing valve63 (Figs. 2 and 4) pipes 23, non-return valves 22 to the cushioncylinders 3 I7. Thereby the free piston assemblies 3Ia, 3Ic, 3Ih areaccelerated towards their inner dead centre position. The inwardmovement of the free piston assemblies causes the link I29 to oscillatethe cam 43 and this affects the operation of the timing valve 53 in thefollowing manner:

When the master starting valve 59 is closed and thus prevents airreaching the valve casing 63, the valve 64 is biassed to the positionshown in Fig. 2, and, on a larger scale in Fig. 4, by its own weight andthe spring 95. With the valve in this position, the collar 64bmaterially restricts the flow of air past the valve seat when the masterstarting valve 55 is opened, so that the air pressure on its undersidelifts the valve into the fully open position of Fig. 5. The trigger 68,which is pivoted in line with the stem 64a of the valve, on a lever 56is thereby lifted until the said lever abuts against the stop 61a on thelug 6'! on which it is hinged. I The trigger 58 is thus brought into therange of part of the cam 43 and, upon oscillation of the latter, istripped into the position I ly by the operator by switching off the fuelsupshown in Fig. 6 allowing the valve 64 to close completely under theaction of the air pressure In this position the end of the stem 54alocks the trigger 68 in its tripped position where it is out of the wayof the oscillating cam 43'. I

Inward movement of the free piston assemblies .under the action of thecompressed starting air as previously described thus causes the timingvalve 63 to close and cut ofi the air supply. The compressed airadmitted to the cushion cylinders 3I7 expands until it escapes throughthe vent holes 3Im uncovered by the cushion pistons 3Ih towards the endof the inward stroke of the free pistons. Movement of the pistons 3Ictinwards causes air to be trapped and compressed in the engine cylinder3Ib and at the end of the inward stroke, fuel is injected by the fuelpump 26 through the injectors 3 It thus causing the engine to start.

The reciprocation of the free piston assemblies oscillates the pistonvalve 39 of the running indicator 31 thereby causing the pipe system I33to be connected to the sump as described. Removal of pressure from pipeI33 enables the piston I34 of the end of stroke indicator to remain inits left-hand position out of the way of the oscillating cam 43.

As soon as the en ine starts, the operator releases the extension 5lla(Fig. 2a) (or the automatic control means will act as described below),the piston valve moves to the ri ht as shown) under the bias of itsspring 5I. and the fluid pressure from the servo-motor cylinder willescape past the left-hand end of piston 50 to the sump at E.Consequently the master starting air valve 59 will close under its ownweight and the action of the air pressure on its top, and the timingvalve 64 will return under its spring bias to the fully releasedposition as shown in Figs. 2 and 4.

If the gas generator is stopped, either manualply to the pump 26 orautomatically as will be described later. the cvcle of operations forsetting the as generator into a state of readiness for restarting. andof starting-proper is automatically repeated as described hereahove.This description was given for the sake of com leteness only, any othersuitable system of starting being ap plicable.

Returning now to the invention proper, it will be remembered t at it isits ob ect to maintain a smooth speed-load characterist c under anycircumstances, no matter how many gas generators are s aring the loadwithin their capacity whether one or more are started or shut down bythe operator or automatically or in what succession.

Th s is illu trated in the dia ram of Fig. 7 in which the turbine speedsare plotted as ordinates and the loads on the turbine as abscissae. Itis again assumed for example that there are three gas generators ofequal capacity and their ranges are indicated so as cumulatively tocover the full turbine load. With the control devices hitherto known,the turbine would follow the speed load characteristic as indicated indotted lines: with one gas generator only in operation the turbine speedwould fall from maximum (within the governor speed range) to minimumalong the line AB. If now a second generator were started to cope withany further increase of turbine load, the turbine speed would suddenlyrise to the point E as will be explained more fully later.

This process would repeat itself with the second and any further gasgenerator beingstarted, the turbine speed followingthe line ECFD; andwould proceed'in the opposite sense with one generator after the otherbeing shutdown. The resulting saw toothcharacteristic would be mostundesirable. The invention aims at establishing the smoothcharacteristic represented by the full line AD as the workingcharacteristic of the'plant, without any substantial change of speedupon change of number of gas generators in operation.

Referring now to Fig. i, in carrying out the invention, the governorloading is decreased progressively asvarying numbers of gas generatorscome into action, the loading being adjusted in accordance with thepower output for which the combination of gas generators is adjusted. Tothis'end, the governor loading spring 2 is compressed between thegovernor. collar and an arm fiipivoted at O and itself loaded by anotherspring Ill which be called the speed-control spring. (Speed governorsthe bias of-which' is variable by the variation of hydraulic pressure ona piston serving as. an abutment for thegovernor spring are known inthemselves, and do not as such form part of the present invention. Threeloading pistons H, l2 and it-corresponding respectively togas-generators 3i, stand 33-are also connected to arm 9 such thatapplication of fluid under pressure to the cylinders Ha, Ha andlta inwhich these pistons move will tend to move the arm 9 against'the forceof spring lii'in a direction to decrease the compression of the loadingspring 2 and thus decrease the loading of the governor i. The-valvemember 5a of the distributing valve 5 is also attached to and actuatedby the arm 9 but preferably; for reasons given hereinafter, throughmeans it allowing a certain definite amount of lost motion.

The'pipe 51 goes also directly from the pipe to to the cylinder lie. Thearm 9 can move the distributing valve member to to different positionswhereb the'pipe i'is connected to the servomotors B (Fig. 2) so as tocontrol one, or two, 01' all three gas-generators. and at the same timeisconnected to each in turn of'the associated cylinders lid; 20., andi302:

Three-way cocks C5 to C3 are included in the pipes la; 3c, and ie, andlocking devices in the form of screws S! and S2 engaging-with annulargrooves in the rod R are incorporated in the mech- 7 anism attached tothe valve member 5a. The function of these parts will be explained laterbut forthe inoment'it should be assumed that the three-way cocks are setas'shown, the inner sleeve Hid of the lost motion device is locked tothe rod R by the screw Si, while the screw S2 is withdrawn to allowmovement'of the valve member 5a.

Assume that the plant is running with only gasgenerator iii inoperation, the fuel pump device is determining the outputof thisgenerator being controlled by the servo-motor 6; The latter i'sconnectedto the source of fiuidpressure on a decrease in turbine speed. Theservo-motor 6 and the fuel pump device 26 willmoveprogressiveiv toincrease the output during such connection the source of fiuid pressure;during such movement the pressure will be prcgressively in creased inthe servo-motor cylinder since the spring is further compressed and, dueto its ordinary spring characteristic; provides a greater force to beovercome'by the hydraulic pressure acting on piston to. On. repeateddecrease in speed of the turbine the servo-motor twill moveprogressively until the output of the gas-generator 3| hasreached. amaximum.. At the .same time 8 the pressure in the cylinder I la willprogressively increase, thereb moving the arms toincrease progressivelythe deflection of spring l8 and to decrease progressively'the deflection.of spring 2, thereby reducing the loading of the governor I.Consequently the turbine speed after each increase of load on theturbine tends to settle at a value less than the previous steady runningspeed, the governor thus givin the engine the predetermined droopingspeed-load characteristic as shown in the left-hand part of Fig. '7 infull line.

The continued movement of the governor arm 9 has moved the distributingvalve member 5a. On a further decrease in turbine speed withgasgenerator 3% operating at its maximum output, the movement of the armconsequent on a further increase in the pressure in the cylinder H awill bring the valve member 5a to a position to put pressure fluid fromthe supply pipe 4 into communication with the fluid servo-notor 6 ofanother gas-generator 32 of the same design as shown in Fig. 2 icrthegas-generator 3!. This communication is established. through pipes 4cand id (corresponding to pipes, Mend 4b of generator 3i) and at the sametime communication is established with the loading cylinder |2a throughpipe lg, the effect of which will be described later.

The pressure reaching the servo-motor cylinder 6 pushes the piston to tothe right against the bias of spring 2817, and therefore adjusts thefuel pump 2% from"no fuel to fuel deiivery. If the initial setting ofthe fuel rack 26a depended solely on the pressure in the cylinder 6',the fuel pump would immediately be adjusted to supply the same amount offuel per strokeas that of the gas-generator already in action. It'isdesirable, however, to start the generator 32 on a minimum fuel settingjust sufficient to bring it into operation without subjecting'it to asudden and exeessive starting load. This is accomplished by provision ofthe cylinder 36, its associated piston i3! and spring 38; With the gasgenerator at rest, the running indicator 37' will supply pressure topipe 533 and hence to cylinder i35 so that'the piston l3? will'be pushedto the left and held in its extreme left hand position by a stop collarformed on the piston rod and abutting against the cylinder cover. Sincethe piston i3? is of larger area than the piston to, the piston rodprojecting from the cylinder I36 will limit the movement of the fuelrack 26a to the minimum fuel position and will hold it in this positionagainst the pressure applied to the pis ton 6a.

Atthe same time the recess 8b of the piston to established connection ofthe pipe system 46, which as will be remembered is under pressureat'this stage, relay E35 being in the position as shown in Fig. 2. andthe running indicator 3! being at rest, withpipe 15' leading to therelay at of the servo-motor for the master starting air valve 553(Fig.2a). Piston 5B'is pushed to the.

left and the same starting procedure is set in motion as describedhereabove with reference to starting manually by pushing in theextension 59a.

When the engine starts the pressure in pipes &6, l5 and I33 is releasedby the "running indicator 3? as described, the air valves and 63 closeas described, and the piston it! moves to the rightunderthe action ofspring I38 thereby permitting the piston Gate take full control of thefuelpump rack 26a.

Returning now to Fig; 1, the immediate tendency for gas-generator 32will be to raise its output to a value substantially equal to that ofgasgenerator 3 I, since the fluid pressure in its servomotor is equal tothat in the servo-motor 6 of gas-generator 3|. The admission of pressurefluid to cylinder 52a has important effects. In the first place, withoutthis cylinder the starting of gas-generator 32 would as mentioned abovewith reference to Fig. 7 tend to bring about a big increase in turbinespeed until eventually this increase was checked by the action of thegovernor in response thereto. The pressure in this cylinder I2a willhowever move piston I2 to increase the stressing of spring in and reducethe loading of the governor by the spring 2 to an extent dependent uponthe actual combined output for which the two gas-generators 3i and 32are momentarily adjusted. This decrease in the loading of the governorwill cause the governorwithout necessarily any increase in speed of theturbine-to respond immediately and move valve 3 to connect the supplypipe 4 to sump, thereby tending to reduce the output for which bothgasgenerators are adjusted and again to increase correspondingly theloading of the governor before the considerable momentary increase intotal output of the gas-generators can be effective to produce anyconsiderable rise in turbine speed. This action will go on until theturbine has settled at a speed which, due to the effect of cylinder l2a,will be slightly less than the prevlous steady running speed, whereuponthe governor valve 3 will reclose. Since the cylinders Hav and |2a andthe servo-motors 5 of both gasgenerators 3|, 32 will all be subject tothe same fluid pressure, both gas-generators will be at all timesadjusted to give approximately the same output, and the loading of thegovernor will be adjusted in accordance with the combined output. Ifthis were not so, there would be an abrupt transition to a differentspeed-load characteristic (Fig. 7) and if the starting of thegas-generator 32 were in response to only a small increase in the loadon the turbine the final steady speed of the turbine at such higher loadwould be higher than its speed at the slightly lower load. Consider, forexample, what would take place if the output control members of thegas-generators were directly connected to the governor so as to take uppositions according to the height of the governor which would hencemaintain an inherent drooping speed-load characteristic. Referring toFig. 7 the speed load characteristic for the plant with three generatorsin action from full load down to no load is represented by the 1 fullline DA and a distance such as GF on, say, the load ordinate representsthe fuel rack setting at that load. Similarly I-lJ represents the racksetting at A; load on the turbine. With only two generators in action(from two-thirds full load down to no load) the speed loadcharacteristic would follow the dotted line CA; the rack setting at A;load on the plant would be GC and at load it would be HE. With only onegenerator in action from full load down to no load, the dotted curve BAwould be followed and the rack setting would vary from a maximum equalto HB down to zero at no load.

Therefore with only the generator 3! in operation and with the load onthe plant increasing, the line AB would be followed. On the starting ofthe gas generator 32, at the point B the fuel rack setting would have todecrease from HR to HE and hence the governor height would also have todecrease correspondingly. This would mean a sudden and abrupt change ofspeed (an increase) corresponding to EB. Hence the speed loadcharacteristic maintained by the governor would vary with the number ofgas generators in operation. There would be a similar result if only onecylinder Ila were provided in Fig. 1. These abrupt changes ofcharacteristic, usually undesirable and sometimes inadmissible, areavoided by the provision according to the invention of cylinders l2a,I3a, etc.

Assuming a subsequent further slight decrease in turbine speed, thevalve 3 will again. connect pressure fluid to the valve 5, to theservo-motors 6 of the gas-generators 3| and 32, and tothe correspondingcylinders Ila and 12a. This will actuate both control servo-motors toincrease the output of both gas-generators 3i and 32 and at the sametime will again move the governor loading arm 9 to cause a correspondingdecrease in the governor loading. The output of the two gas-generatorswill increase until the turbine speed is back to a value again slightlless than the previous steady running value and cor responding to thenew loading of the governor, when the plant will again settle down tosteady conditions. Further decreases of speed will eventually result invalve member 5a reaching such a position (as shown in Figure 1) thatpressure fluid is applied simultaneously to the servo-motor 6 and to thecorresponding cylinder |3a of the corresponding gas-generator 33. Thestarting of this gas-generator will again be accompanied by an abruptdecrease in the governor loading, by an immediate fall of the governorand by a decrease in the outputs of the gasgenerators 3i and 32 untilthe load is approximately shared between the three gas-generators.

It will be appreciated that the output of any one gas-generator will besubstantially in accordance with the pressure of the fluid in each ofthe cylinders I la-l 3a and hence also the force exerted on the governorarm 9 by each of the pistons ll-l3. The total combined output willdepend upon the product of the fluid pressure by the number ofgas-generators in operation. The total force exerted by the loadingpistons will depend upon the product of the fluid pressure and thenumber of pistons in action and hence as stated above should besubstantially proportional to the total combined output of the threegas-generators, thereby causing the load speed characteristic to followthe full-line curve AD of Fig. 7.

On an increase in turbine speed, the valve 3 will connect the sump tothe distributing valve 5 and to those of the servo-motors 6 and thecylinders l Iii-43d which are in action. The output of thegas-generators will accordingly be decreased while the stressing of thespring ID will be correspondingly decreased and the loading of thegovernor by spring 2 correspondingly increased. The distributing valve 5will move until steady conditions are restored and if necessary willmove far enough to disconnect one of the servo-motors 5 and itsassociated governor loading cylinder from the governor valve 3 andconnect them directly to the sump whereby as a result that particulargas-generator is shut down.

When operating at a power close to the critical value at which an extragas-generator is brought into or put out of operation, it wouldobviously be inconvenient if this gas-generator were to be repeatedlybrought into operation and then shut down in response to relativelyminute fluctuall tions in load. To prevent this, the lost motion device!is introduced as mentioned above in the linkage between'the .lever 9 andthe distributing valve 5, whereby there will be an overlap between theload 'at "which any of the gasgenerators is shut down and the load atwhich that gas-generator is re-started.

Fig. la shows a modification wherein the adjustment of the governoriseilected not byvarying the governor loading but by varying theposition of valve 3 relatively to the governor. To this end the valve 3is not connected directly to the governor 2 but is pivotally connectedto the arms which is also pivotally connected at other points to thegovernor, to the assembly of pistons ii, i2 and IS and to the lostmotion device M but is not connected toany fixed pivot. The figure showsonly the governor, the valve '3, the arm e and the spring ld all theother parts being precisely as shown in Fig. 1.

With this arrangement a decrease of turbine speed causes the governor torock the arm 9 about its pivotal connection to the piston assembly or tothe lost motion connection I4,

thereby acting as before to open the valve 3 and i admit fluid pressureto the pipe i. The pressure fluid admitted to cylinder Ha and also tocylinders ifia'and ltc when connections are established to these by thedistributing va lve ii raises the pistons ll, 52 and 53 against theforce of the spring iii but in this arrangement this has no effect onthe loading of the governor. The point of pivotal connection of the arm'9 to the piston assembly is, however, thereby raised with the resultthat the valve 3 is raised relatively to the governor and willaccordingly be restored to its normal closed-position at aslightly lowerspeed of the turbine than before. Thus the same result is achieved of aprogressive -de crease in the speed of the turbine with-increase in theoutput of thegas-generators.

It will be clear from the foregoing description how the invention can beapplied to' the control of any number of gas-generators supplying oneturbine or supplying separate turbines on a common shaft or otherwisemechanically coupled.

Fig. 1 shows a change-over valve 35 of conventional type having a rotorwith a duct .filia connecting pipes la and 4b (which enter the.generators can be varied and any given gas- .generator caused to startup first and shut down last. By this means the running hours of thevarious gas-generators may be approximately equalised.

The provision of the three-way cocks Ci, C2,

C3, the inner sleeve Ma on the rod R and the locking screws Si and S2enable the gasgenerators to be started up and shut down in any order, sothat if desired the first to start up may be made the first to shu-ltdown.

In carrying out this feature of the invention, the valve member 5a islocked in position by tightening the screw S2 on to the rod R and theinner sleeve E ia of the lost motion device is allowed to movefreely onthe rod R by unscrewing Si. If, for example, it is desired to operatethe generator 33 and keep the remaining two out of action, the three-waycock C3 is turned to the position shown in Fig. 1 whereby communicationis established between pipe 4, the servomotor 6 of generator 33 and thecylinder l3a, the other two cocks Cl and C2 are turned anti-clockwisethrough one quarter of a turn whereby the servomotor 8 of the generators3i and 32 and the cylinders Ila and IM are opened to drain.

The shutting-off of a gas generator can be effected manually asmentioned hereabove by interrupting the fuel supply to it. Thisshuttingoff is effected automatically according to the invention in thefollowing manner:

Assuming thatall three generators are in operation, that the valvemember 5a is arranged for automatic operation by the arm 8 and the lostmotion device it and that the three-way cocks Ci, C2, C3 are inthe'position shown in Fig. l, decreasing load on the plant will causethe member 5a to fall, since increasing speed of the turhine will causethe governor to lift the valve 3 and open pipe 4 to drain. If thedecrease in load is of such magnitude that the top edge of the valvemember uncovers the pipe ie, the cylinder lite and the servo-motorcylinder t of the generator 33 will be drained through the upper ventingport 5?) of the cylinder 5. The spring 261) will thus be enabled to movethe fuel rack of the pump 28 to its no fuel position and stop theassociated generator 33. Further reduction in load will cause the member5a to fall still more until itstop edge uncovers the pipe to, and socauses the generator 32 to be shut down.

If the plant is operating with the valve member 5a looked in placeashereinbefore described, the gas generators may be shut down in any orderby turning one or more of the three-way cocks Cl, C2, C3 into suchposition that the servo-motor cylinder-5 of its associated free pistonunit is connected to drain.

It will be understood that the individual gasgenerators can be broughtinto and out of action either sequentiallyin which case the sequence canbe altered at will by a device such as the change-over valve-35described hereabove-or in any other way, if desired haphazardly or byreasons not connected with the load on the prime mover. Such reasons maybe for example the shutting down of a gas-generator for inspection orrepair or thewarming up of a gas-generator which had not been inoperation for some time, to make it ready for operation at full outputif desired.

In whichever way or by whatever reason the change in the number ofgas-generator units is effected, the result will always be thatdescribed hereabove, namely, the provision of a governing system whichmaintains a predetermined speed at any given load, which speed will bemaintained unchanged by the'starting up of additional generators or theshutting down of gas generators, within the limits imposed bythe'maximum load carrying capacity of the generators remaining inservice.

What we claim-as our invention and desire to secure by Letters Patentis:

1. A power "plant comprising in combination a prime mover, aplurality'of internal combustion engine-driven compressor devicessupplying motive fluid in common to said prime mover, a speedgovernoractuated by the prime mover, a

separate fuel regulator for each of said compressor devices, a speedadjuster for said governor responsive to the combined power supplied bysaid compressor devices, and comprising a plurality of pistons andcylinders together constituting the motive part of said speed adjusterand respectively corresponding in number to the number of independentactuators hereinafter mentioned, a plurality 'of fluid pressure motorseach constituting an independent actuator for each of the said fuelregulators, all of said actuators being under the control of said speedgovernor, a governor actuated valve, a distributing valve actuated bysaid speed adjuster, a fluid supply connection going through saidgovernor actuated valve to said distributing valve, and a separateoutlet pipe to each said actuator from said distributing valve, saiddistributing valve having progressive positions wherein the fluid supplyconnection is connected to one actuator only, then to the first and asecond and so on up to the maximum.

2. Power plant comprisingin combination a prime mover, a plurality ofinternal combustion engine-driven compressor devices supplying motivefluid in common to said prime mover, at least part off said compressordevices being capable of being put in and out of operation during theoperation of the said prime mover, when the load on the said prime moverpermits, a speed governor actuated by the prime mover, a separate fuelregulator for each of said compressor devices, independent actuators foreach of said fuel regulatorsjjall said actuators being under the controlof said speed governor and lastly a speed adjuster for said governorresponsive to the combined power supplied by said compressor devices,irrespective of the number of said compressor devices in operation.

JOHN PICTON CHITTENDEN.

ROBERT JAMES WELSH.

REFERENCES CITED I The following references are of record in the

